Yes, that is poly fill...but a white fluval pad is much better, and not so stringy and loose. Those bags of polyfill were the rave for a week or two, and they work, but they stick to bridges, and the fibers are really loose, so they can float around and drift pretty easily. Your better off just removing half teh factory batting from your cart. That stuff can be rinsed and reused generally for as long as the cart itself lasts. BUt the general issue with factory carts is the filler being too dense to work well, so just lighten it up by half, and I think you'll be happy.